1. Field of the Invention
The present invention relates to a single electron transistor wherein single electron tunneling (hereinafter referred to as SET) phenomena can be generated at room temperature.
2. Description of Related Art
The single electron transistor has been considered as a substitute for MOSFET, which is the leading device of a Solid State transistor, because the demand for super miniaturization in a size of less than a submicron can be realized by application of SET to molecule devices.
Hitherto, the single electron transistor has been made containing a quantum dot means composed of polycrystalline silicon having a size of 5-8 nm in width, 10-20 nm in height and about 100 nm in length as reported in Appl. Phys. Left. 65(5), 1 August 1994, p.624. Theoretically, a possible application of SET to molecule devices is proposed by Yasuo Wade in "Principle of Single Electron Tunneling Phenomena and Possible Application to Molecule Device" published in the TECHNICAL REPORT OF IEICE, OME 93-59. The single electron transistor was fabricated as shown in FIG. 3 by firstly connecting three polyacetylene conductors A1, A2 and A3 through a pair of polyethylene insulators E1, E2 used as a tunnel junction, and secondly connecting the middle conductor A3 through a third polyethylene insulator E3 to a fourth polyacetylene conductor A4. It was reported that the opposite end conductors A1 and A2, respectively, act as an electrode, the middle conductor acts as the quantum dot means and the fourth conductor acts as a control gate.
However, where the quantum dot means is a semiconductor made of polycrystalline silicon doped with phosphorus P, the nearest transition level to the Fermi level is less than a level (.DELTA.E=about 25 mV) of electron thermal excitation at room temperature. Accordingly, in order to generate the SET phenomena in such devices, the devices must be cooled to about 4K, resulting in an impractical operating condition.
On the other hand, where the quantum dot is composed of polyacetylene, the SET phenomena at room temperature can be theoretically generated but there is no disclosure of how to set the transistor assembly and how to make each means to be fixed.